Hi - just joined BF yesterday. Used to ride a lot in teens and early 20's, Mostly got out of it for a while after college, but got back into riding when I bought a friend's MTB 10 or so years ago.
Did a bit of commuting the past couple of years on an old MTB with slicks, but this year decided to start riding more and got a great deal on Craigslist (not often you can say that) -- a 2007 TriCross Comp that had less than 20 miles on it for $900. They guy rode it home from the shop, then rode it once more and decided he wasn't going to get into it so it sat in his spare bedroom for 18 months. No wear on the tires, not a single scuff, scratch or spec of dirt (except dust from sitting) on the bike. I even checked with the shop to verify he bought it there, cause he knew nothing about it and I thought it might be stolen.
Anyway, I love the "new" bike, and commute at least three times a week (27m round trip) and more if I can.
As for MTB, I'm riding a MT Cycle San Andreas that I bought from a buddy a couple years ago -- couldn't pass it up for $300.
I put new handlebars and clipless pedals on the San Andreas. New pedals on the TriCross. Both pics below are before I did anything to the bikes.
The San Andreas is a bit of an odd ride. It's very high, and took some getting used to -- but it's good...for now.
The TriCross fits me perfectly, and rides like buttah.